In a vehicle engine, a small amount of unburned fuel and exhaust gases will escape around the piston rings during combustion and enter the crankcase. The fuel and gases are referred to as blow-by gas and the vehicle includes a crankcase ventilation system to deal with the blow-by gas. To reduce emissions to the atmosphere, the blow-by gas is typically recycled back into the combustion chamber of the engine. This is done by mixing the blow-by gas with intake air, upstream of the turbocharger if the engine includes this. The blow-by gas, and thus the mix of blow-by gas and intake air, contains oil from the crankcase. The intake air can contain moisture, snow and the like, depending on the environmental conditions.
An oil and water separator is often present upstream of the turbocharger to reduce the amount of water and oil present in the air flowing towards the combustion chamber. Nevertheless, even if a separator is used, the blow-by gas can contain water which can freeze to ice if the vehicle is in a cold environment. This ice can hinder air flow in the ducting or form pieces of ice chunks which can cause damage to components, such as the compressor vanes of the turbocharger. The forming of ice can occur while the engine is switched off or idling.
A sump may be provided in the air ducting and ice can form here when oil vapour enters the ducting and encounters the cold air stream. Since the water/ice has an oil content, and the ducting has an oil coating, the ice tends not to adhere to the inner surface of the ducting and is therefore drawn into the turbocharger, particularly during high acceleration.
It is desirable to provide improved means of inhibiting the formation of ice and/or inhibiting the formed ice from flowing downstream, such as to the turbocharger.